Reciprocating refrigerant compressor

ABSTRACT

An inlet port  15  is divided into a plurality of holes  15   a,    15   b,    15   c,    15  by ribs  61   a,    61   b,    61   c.  For example, when liquid refrigerant is compressed within a compression chamber, the inlet valve  21  receives excessive load which is about to bend the inlet valve  21  largely toward the suction chamber side. However, the inlet valve  21  is supported by the ribs  61   a,    61   b,    61   c,  and therefore the inlet valve  21  is hardly bent, but the inlet port  21  is positively closed.

TECHNICAL FIELD

[0001] This invention relates to a reciprocating refrigerant compressorused as a refrigerant compressor for an automotive air conditioner, andmore particularly to a reciprocating refrigerant compressor of a type inwhich pistons reciprocate, such as a wobble plate compressor and a swashplate compressor.

BACKGROUND ART

[0002] A wobble plate compressor includes a cylinder block having aplurality of cylinder bores, a plurality of pistons for reciprocatingwithin the respective cylinder bores, a cylinder head secured to an endface of the cylinder block via a valve plate, and a plurality of inletvalves for opening and closing a plurality of inlet ports formed throughthe valve plate.

[0003] Within the cylinders are formed compression chambers,respectively, and the volume of each compression chamber varies with themotion of a piston associated therewith.

[0004] The cylinder head has a suction chamber formed therein forreceiving low-pressure refrigerant gas flowing therein from anevaporator side.

[0005] The number of the inlet valves and the number of the inlet portsformed through th valv plat are equal to the number of th cylinderbores, similarly to the number of the compression chambers and thenumber of the pistons.

[0006] The suction chamber communicates with the compression chambersvia the inlet ports.

[0007] During the suction stroke, as the volume of a compression chamberprogressively increases, the inlet valve is bent toward the compressionchamber side to open the inlet port, via which refrigerant gas in thesuction chamber is drawn into the compression chamber.

[0008]FIG. 12 is a fragmentary enlarged plan view of a valve plate of aconventional wobble plate compressor.

[0009] A valve plate 702 is formed with inlet ports 715, and outletports 716 are formed inward of the inlet ports 715 (radially inward inthe valve plate 702). Further, the inlet ports 715 and the outlet ports716 are located inward of respective opening edges 706 a of the cylinderbores. An inlet valve 721 is formed with a hole 763, such that theoutlet port 716 is prevented from being closed by the inlet valve 721.

[0010] The opening edge 706 a of the cylinder bore is formed with astopper recess 770 at a location opposed to an end portion 721 a of theinlet valve 721.

[0011] As the piston moves toward the bottom dead center position duringthe suction stroke, the difference in pressure between the compressionchamber and the suction chamber is increased, whereby the inlet valve721 is bent toward the compression chamber side to open the inlet port715, via which refrigerant gas in the suction chamber is drawn into thecompression chamber. At this time, the end portion 721 a of the inletvalve 721 abuts on the stopp r r cess 770, which limits the bend of theinlet valve 721.

[0012] The dimension of depth of the stopper recess 770 (length from anend face of the cylinder block to the bottom surface of the stopperrecess 770) is configured to be small to thereby reduce the suctionpulsation.

[0013] As the piston moves toward the top dead center position duringthe compression stroke, the volume of the compression chamber isprogressively reduced to increase the pressure in the compressionchamber. At this time, the inlet valve 721 is brought into intimatecontact with the valve plate 702 by high pressure to close the inletport 715.

[0014] However, if the dimension of depth of the stopper recess 770 issmall, the suction efficiency is lowered, which degrades the performanceof the refrigerant compressor.

[0015] To improve the performance of the refrigerant compressor, it isnecessary to increase the area of an opening formed during suction ofrefrigerant. To meet this requirement, it is necessary to increase thearea of the inlet port 715. If the area of the inlet port 715 isincreased, it is necessary to enlarge the inlet valve 721 accordingly.

[0016] However, if the area of the inlet port 715 is increased, duringliquid compression in which liquid (liquid refrigerant) is compressedwithin the compression chamber, excessive load is applied to the inletvalve 721, which sometimes causes leakage of the liquid into the suctionchamber side, or deformation or breakage of the inlet valve 721.

[0017] It is an object of the inv ntion to provide a reciprocating rfrig rant compressor that is capable of increasing the ar as of inletports, and at the same time preventing leakage of liquid into thesuction chamber side and deformation and breakage of inlet valves.

DISCLOSURE OF THE INVENTION

[0018] To attain the above object, a reciprocating refrigerantcompressor according the present invention includes a cylinder blockhaving a plurality of cylinder bores formed therein, a cylinder headsecured to an end face of the cylinder block via a valve plate, alow-pressure chamber formed within the cylinder head, a plurality ofinlet ports formed through the valve plate, for communicating betweenthe low-pressure chamber and the cylinder bores, and a plurality ofinlet valves for opening and closing the inlet ports, a number of theinlet ports and a number of the inlet valves being both equal to anumber of the cylinder bores, wherein the inlet ports are each dividedinto a plurality of holes by ribs.

[0019] For example, when liquid is compressed within a compressionchamber, excessive load is applied during the compression stroke to aninlet valve whereby the inlet valve is about to be largely bent towardthe suction chamber side. However, the inlet valve is supported by theribs, which restricts excessive bend of the inlet valve. Therefore, evenwhen the area of the inlet port is increased, it is possible to preventleakage of liquid refrigerant into the suction chamber side, anddeformation and breakage of the inlet valve.

[0020] Preferably the ribs are formed substantially radially from a cntral axis of the cylinder bore.

[0021] Since the ribs are formed substantially radially from a centralaxis of the cylinder bore, as describe above, the ribs do not offersignificant resistance to the refrigerant gas, so that the inflow ofrefrigerant gas becomes smooth.

[0022] Preferably, the ribs have a surface formed with a groove or ahole.

[0023] Since the ribs have a surface formed with a groove or a hole, asdescribed above, lubricating oil collected between the inlet valve andthe valve plate is discharged via the grooves or the holes. Therefore,it is possible to prevent delay of timing in which the inlet valve opensduring the suction stroke.

[0024] Preferably, the ribs are formed substantially radially from acentral axis of the cylinder bore, and the ribs have a surface formedwith a groove or a hole.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a perspective view showing a valve plate and a valvesheet of a wobble plate compressor according to a first embodiment ofthe present invention;

[0026]FIG. 2 is a plan view of the valve plate shown in FIG. 1;

[0027]FIG. 3 is a fragmentary enlarged view of the valve plate shown inFIG. 2;

[0028]FIG. 4 is a longitudinal cross-sectional view of a wobble platecompressor according to the first embodiment of the present invention;

[0029]FIG. 5 is a fragmentary enlarged plan view of a valve plate of awobble plate compressor according to a second embodiment of the presentinvention;

[0030]FIG. 6 is a fragmentary enlarged plan view of a valve plate of awobble plate compressor according to a third embodiment of the presentinvention;

[0031]FIG. 7 is a perspective view showing a valve plate and a valvesheet of a wobble plate compressor according to a fourth embodiment ofthe present invention;

[0032]FIG. 8 is a plan view of the valve plate;

[0033]FIG. 9 is a fragmentary enlarged plan view of a valve plate of awobble plate compressor according to a fifth embodiment of the presentinvention;

[0034]FIG. 10 is a fragmentary enlarged plan view of a valve plate of awobble plate compressor according to a sixth embodiment of the presentinvention;

[0035]FIG. 11 is a fragmentary enlarged plan view of a valve plate of awobble plate compressor according to a seventh embodiment of the presentinvention; and

[0036]FIG. 12 is a fragmentary enlarged plan view of a valve plate of aconventional wobble plate compressor.

BEST MODE FOR CARRYING OUT THE INVENTION

[0037] The invention will now be described in detail with reference todrawings showing preferred embodiments thereof.

[0038]FIG. 4 is a longitudinal cross-sectional view of a wobble platecompressor according to a first embodiment of the invention. FIG. 1 is aperspective view showing a valve plate and a valve sheet of the wobbleplate compressor. FIG. 2 is a plan view of the valve plate shown in FIG.1, and FIG. 3 is a fragmentary enlarged view of the valve plate shown inFIG. 2.

[0039] This compressor has a cylinder block 1 having one nd thereofsecured to a rear head (cylinder head) 3 via a valve plate 2 and theother end thereof secured to a front head 4.

[0040] The cylinder block 1 has a plurality of cylinder bores 6 axiallyextending therethrough at predetermined circumferential intervals aboutthe shaft 5. Each cylinder bore 6 has a piston 7 slidably receivedtherein. The cylinder bore 6 defines a compression chamber 60 therein,the volume of which is changed with motion of the piston 7. An openingedge 6 a of the cylinder bore 6 is formed with a stopper recess 70, at alocation opposed to an end portion 21 a of an inlet valve 21, forlimiting the bend of the end portion 21 a of the inlet valve 21 (seeFIGS. 2 and 3). The stopper recess 70 limits the amount of bend (openingdegree) of the inlet valve 21.

[0041] Within the front head 4, there is formed a crankcase 8 withinwhich a wobble plate 10 is accommodated for performing wobbling motionabout a hinge ball 9 in a manner interlocked with the rotation of theshaft 5.

[0042] Within the rear head 3, there are formed a discharge chamber 12and a suction chamber 13 located around the discharge chamber 12.

[0043] The valve plate 2 is formed with a plurality of outlet ports 16for communicating between the cylinder bores 6 and the discharge chamber12, and a plurality of inlet ports 15 for communicating between thecylinder bores 6 and the suction chamber 13, at predeterminedcircumferential intervals. The outlet ports 16 are opened and closed bythe outlet valves 17, and the outlet valves 17 are fixed to the rearhead-side end face of the valve plate 2 together with a valve retainer18 by a rivet 19. Further, the inlet ports 15 are opened and closed bythe inlet valves 21, and the inlet valves 21 are disposed between thevalve plate 2 and the cylinder block 1. The discharge chamber 12 and thecrankcase 8 are communicated with each other via a passage 79 and anorifice 80.

[0044] The respective numbers of the inlet valves 21, the outlet valves17, the inlet ports 15, the outlet ports 16, and the compressionchambers 60 are equal to the number (5 in this embodiment) of thecylinder bores 6.

[0045] As shown in FIGS. 1 and 2, the inlet ports 15 and the outletports 16 are located, inward of the opening edges 6 a of the cylinderbores 6, respectively. Further, the inlet ports 15 are located outwardof the outlet ports 61 (radially outward in the valve plate 2). The fiveinlet ports 15 are each formed by a plurality of holes 15 a, 15 b, 15 c,15 d. In other words, the holes 15 a, 15 b, 15 c, 15 d form one inletport 15. The sum total of respective areas of the holes 15 a, 15 b, 15c, 15 d forming one inlet port 15 is larger than the area of the inletport 715 of the prior art (see FIGS. 3 and 12). In accordance therewith,the end portion 21 a of the inlet valve 21 is larger than the endportion 721 a of the inlet valve 721 of the prior art.

[0046] The holes 15 a, 15 d are generally semi-circular, and the holes15 b, 15 c are generally sector-shaped. The holes 15 a, 15 b, 15 c, 15 dare arranged along the opening edge 6 a of the cylinder bore 6. Theholes 15 a and 15 b, the holes 15 b and 15 c, and the holes 15 c and 15d are adjacent to each other via ribs 61 a, 61 b, 61 c, respectively.

[0047] As shown is FIG. 1, the five inlet valves 21 are integrallyformed with a valve sheet 62. Each inl t valve 21 is form d with a hole63, which prevents the outlet port 16 from being closed by the inletvalve 21.

[0048] The cylinder block 1 is formed with a communication passage 31communicating between the suction chamber 13 and the crankcase 8, and apressure control valve 32 is arranged across an intermediate portion ofthe communication passage 31, for control of pressure in the suctionchamber 13 and pressure in the crankcase 8.

[0049] Further, the front-side end of the shaft 5 is rotatably supportedby a radial bearing 26 arranged in the front head 4, and the rear-sideend of the shaft 5 is rotatably supported by a radial bearing 24 and athrust bearing 25. The shaft 5 has a thrust flange 40 fixed thereon, anda drive hub 41 mounted thereon via the hinge ball 9 which is axiallyslidable. The thrust flange 40 is supported on the inner wall of thefront head 4 via a thrust bearing 33. A portion of the thrust flange 40and a portion of the drive hub 41 are connected by a linkage 42 viawhich the rotation of the shaft 5 is transmitted from the thrust flange40 to the drive hub 41. The wobble plate 40 is relatively rotatablymounted on the drive hub 41 via a radial bearing 27 and a thrust bearing28. The wobble plate 10 is connected to the pistons via connecting rods11.

[0050] Between the hinge ball 9 and a boss 40 of the thrust flange 40, acoil spring 44 is interposed as a destroke spring, and the hinge ball 9is urged toward the cylinder block 1 by the coil spring 44.

[0051] Further, a fixed washer 45 is fixedly fitted on the shaft 5 at alocation toward the cylinder block side, and b tween the fixed wash 45and the hinge ball 9, a plurality of curved springs 46 and a coil spring47 as destroke springs are interposed in series, for urging the hingeball 9 toward the thrust flange 40.

[0052] Next, the operation of this wobble plate compressor will bedescribed.

[0053] As torque of an engine, not shown, installed on a vehicle, notshown, is transmitted to the shaft 5, the thrust flange 40 and the drivehub 41 rotate together with the shaft 5, which causes the wobble plate10 to perform wobbling motion about the hinge ball 9. The wobblingmotion is transmitted to the pistons 7 via the connecting rods 11,whereby the wobbling motion is converted to the linear reciprocatingmotion of each piston 7. As the piston 7 reciprocates in the cylinderbore 6, the volume of the compression chamber 60 changes, whichsequentially causes suction, compression, and delivery of refrigerantgas, whereby high-pressure refrigerant gas is delivered in an amountcorresponding to an angle of inclination of the wobble plate 10.

[0054] When thermal load on the compressor decreases and the pressurecontrol valve 32 closes the communication passage 31 to increase thepressure in the crankcase 8, the angle of inclination of the wobbleplate 10 becomes smaller, so that the length of stroke of the piston 7is decreased to reduce the displacement of the compressor. On the otherhand, when thermal load on the compressor increases and the pressurecontrol valve 32 opens the communication passage 31 to reduce thepressure in the crankcase 8, the angle of inclination of the wobbleplate 10 becomes larger, whereby the length of stroke of the piston 7 isincreased to increas the displacement of the compressor.

[0055] In the suction stroke, as the piston 7 moves to the bottom deadcenter position, the difference between pressure in the compressionchamber 60 and pressure in the suction chamber 13 is increased, so thatthe inlet valve 21 is bent into the compression chamber 60 to open theinlet port 15, via which the refrigerant gas in the suction chamber 13is drawn into the compression chamber 60. As described above, the fiveinlet ports 15 are each comprised of a plurality of holes 15 a to 15 d,and the sum total of the respective areas of the holes 15 a to 15 d islarger than the area of the inlet port 715 of the prior art, which makesthe suction efficiency higher than the prior art to improve theperformance of the refrigerant compressor. Further, the flow ofrefrigerant gas drawn in is rectified (this is also the case with athird embodiment of the invention).

[0056] Further, in the compression stroke, as the piston 7 moves to thetop dead center position, the volume of the compression chamber 60 isprogressively reduced to increase the pressure in the compressionchamber 60. At this time, the inlet valve 21 keeps the inlet port 15closed and the outlet valve 17 keeps the outlet port 16 closed. In thedelivery stroke, the volume of the compression chamber 60 becomesminimum, and the pressure in the compression chamber 60 becomes maximum.When there is produced a predetermined differential pressure between thecompression chamber 60 and the discharge chamber 12, the outlet valve 17is bent into the discharge chamber 60 to open the outlet port 16. Atthis time, the inlet valve 21 keeps the inlet port 15 closed. At thistime, the inlet valve is urged against the valve plate 2 by highpressure to keep the inlet port 15 closed.

[0057] Further, when liquid is compressed within the compression chamber60, excessive load acting on the inlet valve 21 is about to largely bendthe inlet valve 21 into the suction chamber 13. However, since the inletvalve 21 is supported by the ribs 61 a, 61 b, 61 c, the bend isrestricted, thereby ensuring the sealing properties.

[0058] According to the first embodiment, even when the area of theinlet port 15 is increased, it is possible to prevent leakage of liquidrefrigerant into the suction chamber 13 and deformation and breakage ofthe inlet valve 21.

[0059]FIG. 5 is a fragmentary enlarged plan view of a valve plate of awobble plate compressor according to a second embodiment of the presentinvention. The construction of the wobble plate compressor is identicalto that of the wobble plate compressor according to the first embodimentexcept for the valve plate, and therefore description thereof isomitted.

[0060] In this embodiment, five inlet ports 115 of the valve plate 102are each formed by three holes 115 a, 115 b, 115 c. The holes 115 a, 115b, 115 c are circular, and are easy to machine. The areas of the holes115 a, 115 c are approximately equal to each other, and the area of thehole 115 b is smaller than that of the hole 115 a. The holes 115 a and115 b, the holes 115 b and 115 c, the holes 115 a and 115 c are adjacentto each other via ribs 161 a, 161 b, 161 c, respectively.

[0061] The second embodiment provides the same advantageous effects asprovided by the first embodiment.

[0062]FIG. 6 is a fragmentary enlarged plan view of a valve plate of awobble plate compressor according to a third mbodiment of the presentinvention. The construction of th wobble plate compressor is identicalto that of the wobble plate compressor according to the first embodimentexcept for the valve plate, and therefore description thereof isomitted.

[0063] In this embodiment, five inlet ports 215 of the valve plate 202are each formed by three holes 215 a, 215 b, 215 c. The holes 215 a, 215c are generally semi-circular, and the hole 215 b is generallysector-shaped. The holes 215 a and 215 b, and the holes 215 b and 215 care adjacent to each other via ribs 261 a, 261 b, respectively.

[0064] The third embodiment provides the same advantageous effects asprovided by the first embodiment.

[0065] It should be noted that the above embodiments have commonfeatures in that the inlet ports 15, 115, 215 are formed by respectivepluralities of holes 15 a to 15 d, 115 a to 115 c, 215 a to 215 c, thata plurality of holes are arranged along the opening edge 6 a of thecylinder bore 6, and that the sum total of respective areas of holesforming one inlet port is larger than the area of one inlet port 715 ofthe prior art (approximately three times larger).

[0066]FIG. 7 is a perspective view showing a valve plate and a valvesheet of a wobble plate compressor according to a fourth embodiment ofthe present invention, and FIG. 8 is a plan view of the valve plate. Theconstruction of this wobble plate compressor is identical to that of thewobble plate compressor according to the first embodiment except for thevalve plate, and therefore description thereof is omitted.

[0067] The valve plate 302 of this embodiment has one linear groove(groove) 64 formed in each of the ribs 61 a, 61 b, 61 c of the valveplate 2 of the first embodiment. In other words, the fourth embodimenthas features in common with the first embodiment in that each inlet port15 is formed by four holes 15 a to 15 d, and that the holes 15 a and 15b, the holes 15 b and 15 c, and the holes 15 a and 15 d are adjacent toeach other via the ribs 61 a, 61 b, 61 c, respectively, but is differentfrom the first embodiment in that the linear grooves 64 are formed inthe respective surfaces of the ribs 61 a, 61 b, 61 c.

[0068] When the inlet valve 21 is in intimate contact with the valveplate 2 to keep the inlet port 15 closed, lubricating oil collectedbetween the inlet valve 21 and the valve plate 2 is discharged throughthe linear grooves 64.

[0069] Therefore, when a predetermined differential pressure is producedbetween the compression chamber 60 and the suction chamber 21 during thesuction stroke, the inlet valve 21 rapidly opens. In this connection,without the linear grooves 64, the lubricating oil between the inletvalve 21 and the valve plate 2 causes the inlet valve 21 to be adsorbedtoward the ribs 61 a, 61 b, 61 c, which sometimes delays the timing inwhich the inlet valve 21 opens, thereby degrading the suctionefficiency.

[0070] It should be noted that the linear grooves 64 are provided onlyin the ribs 61 a, 61 b, 61 c, and therefore, seating properties of theinlet valve 21 on the valve plate 2 are not degraded by the lineargrooves 64.

[0071] The fourth embodiment provides the same advantageous effects asprovided by the first embodiment, and at the same time, due tocapability of preventing delay of timing of opening of th inlet valves21 in the suction stroke, it is possible to enhance the suctionefficiency and improv the performance of the refrigerant compressor.

[0072]FIG. 9 is a fragmentary enlarged plan view of a valve plate of awobble plate compressor according to a fifth embodiment of the presentinvention. The construction of this wobble plate compressor is identicalto that of the wobble plate compressor according to the first embodimentexcept for the valve plate, and therefore description thereof isomitted.

[0073] The valve plate 402 of this embodiment has a plurality of roundholes (holes) 164 linearly arranged in each of ribs 61 a, 61 b, 61 c ofthe valve plate 2 of the first embodiment. In other words, the fifthembodiment has a feature in common with the first embodiment and thefourth embodiment in that each inlet port is formed by four holes 15 ato 15 d, and that the holes 15 a and 15 b, the holes 15 b and 15 c, andthe holes 15 c and 15 d are adjacent to each other via the ribs 61 a, 61b, 61 c, respectively, but is different from the first embodiment andthe fourth embodiment in that instead of the grooves 64 a, 64 b, 64 c, aplurality of round holes 164 are formed in each of the ribs 61 a, 61 b,61 c.

[0074] The fifth embodiment provides the same advantageous effects asprovided by the fourth embodiment.

[0075]FIG. 10 is a fragmentary enlarged plan view of a valve plate of awobble plate compressor according to a sixth embodiment of the presentinvention. The construction of this wobble plate compressor is identicalto that of the wobble plate compressor according to the first embodimentexcept for the valve plate, and therefore description thereof isomitted.

[0076] The valve plate 502 of this embodiment has two linear grooves(grooves) 264 a, 264 b formed parallel to each other in each of the ribs161 a, 161 b, 161 c of the valve plate 102 of the second embodiment. Inother words, the sixth embodiment has features in common with the thirdembodiment in that each inlet port 115 is formed by three holes 115 a to115 c, and that the holes 115 a and 115 b, the holes 115 b and 115 c,the holes 115 c and 115 a are adjacent to each other via the ribs 161 a,161 b, 161 c, respectively, but is different from the second embodimentin that a plurality of linear grooves 264 a, 264 b are formed in each ofthe ribs 161 a, 161 b, 161 c.

[0077] The sixth embodiment provides the same advantageous effects asprovided by the fourth embodiment.

[0078]FIG. 11 is a fragmentary enlarged plan view of a valve plate of awobble plate compressor according to a seventh embodiment of the presentinvention. The construction of this wobble plate compressor is identicalto that of the wobble plate compressor according to the first embodimentexcept for the valve plate, and therefore description thereof isomitted.

[0079] The valve plate 602 of this embodiment has generallytrapezoid-shaped holes 364 a and generally triangular holes 364 b formedin a line in an alternating manner in each of the ribs 261 a, 261 b ofthe valve plate 2 of the third embodiment. In other words, the seventhembodiment has features in common with the first embodiment in that eachinlet port 215 is formed by three holes 215 a to 215 c, and that theholes 215 a and 215 b, and the holes 215 b and 215 c are adjac nt toeach other via the ribs 261 a, 261 b, respectiv ly, but is differentfrom the third embodiment in that the trap zoid-shaped holes 364 a andthe generally triangular holes 364 b are arranged in a line in analternating manner in each of the ribs 261 a, 261 b.

[0080] The seventh embodiment provides the same advantageous effects asprovided by the fourth embodiment.

[0081] It should be noted that in the above embodiments, as the groovesand the holes, there are proposed by way of example, linear grooves 64,264 a, 264 b, round holes 164, and polygonal holes (trapezoid-shapedholes 364 a and triangular holes 364 b), this is not limitative, but instead of these, by increasing the surface roughness of the ribs 61 a to61 c, 161 a to 161 c, 261 a, 261 b through spraying particles onto thesurfaces thereof, it is also possible to realize the same function asoffered by the holes and grooves.

[0082] Although in the above embodiments, as an example of thereciprocating refrigerant compressor, the wobble plate compressor isdescribed, the scope of the present invention is not limited to this,but the present invention can be applied to other reciprocatingcompressors, such as a swash plate compressor.

INDUSTRIAL APPLICABILITY

[0083] As described heretofore, the reciprocating refrigerant compressoraccording to the present invention is useful as a refrigerant compressorfor an automotive air conditioner, and according to this reciprocatingrefrigerant compressor, it is possible to increase the areas of inletports, and at the same time prevent leakage of liquid into the suctionchamb r and d formation and breakage of the inlet valves.

1. A reciprocating refrigerant compressor including: a cylinder blockhaving a plurality of cylinder bores formed therein, a cylinder headsecured to an end face of said cylinder block via a valve plate, alow-pressure chamber formed within said cylinder head, a plurality ofinlet ports formed through said valve plate, for communicating betweensaid low-pressure chamber and said cylinder bores, and a plurality ofinlet valves for opening and closing said inlet ports, a number of saidinlet ports and a number of said inlet valves being both equal to anumber of said cylinder bores, wherein said inlet ports are each dividedinto a plurality of holes by ribs.
 2. A reciprocating refrigerantcompressor according to claim 1, wherein said ribs are formedsubstantially radially from a central axis of said cylinder bore.
 3. Areciprocating refrigerant compressor according to claim 1, wherein saidribs have a surface formed with a groove or a hole.
 4. A reciprocatingrefrigerant compressor according to claim 1, wherein said ribs areformed substantially radially from a central axis of said cylinder bore,and wherein said ribs have a surfac form d with a groove or a hole.